// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SKIA_EXT_BITMAP_PLATFORM_DEVICE_CAIRO_H_
#define SKIA_EXT_BITMAP_PLATFORM_DEVICE_CAIRO_H_

#include <stdint.h>

#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "skia/ext/platform_device.h"

typedef struct _cairo_surface cairo_surface_t;
typedef struct _cairo cairo_t;

// -----------------------------------------------------------------------------
// Image byte ordering on Linux:
//
// Pixels are packed into 32-bit words these days. Even for 24-bit images,
// often 8-bits will be left unused for alignment reasons. Thus, when you see
// ARGB as the byte order you have to wonder if that's in memory order or
// little-endian order. Here I'll write A.R.G.B to specifiy the memory order.
//
// GdkPixbuf's provide a nice backing store and defaults to R.G.B.A order.
// They'll do the needed byte swapping to match the X server when drawn.
//
// Skia can be controled in skia/include/corecg/SkUserConfig.h (see bits about
// SK_R32_SHIFT). For Linux we define it to be ARGB in registers. For little
// endian machines that means B.G.R.A in memory.
//
// The image loaders are controlled in
// webkit/port/platform/image-decoders/ImageDecoder.h (see setRGBA). These are
// also configured for ARGB in registers.
//
// Cairo's only 32-bit mode is ARGB in registers.
//
// X servers commonly have a 32-bit visual with xRGB in registers (since they
// typically don't do alpha blending of drawables at the user level. Composite
// extensions aside.)
//
// We don't use GdkPixbuf because its byte order differs from the rest. Most
// importantly, it differs from Cairo which, being a system library, is
// something that we can't easily change.
// -----------------------------------------------------------------------------

namespace skia {

class ScopedPlatformPaint;

// -----------------------------------------------------------------------------
// This is the Linux bitmap backing for Skia. We create a Cairo image surface
// to store the backing buffer. This buffer is BGRA in memory (on little-endian
// machines).
//
// For now we are also using Cairo to paint to the Drawables so we provide an
// accessor for getting the surface.
//
// This is all quite ok for test_shell. In the future we will want to use
// shared memory between the renderer and the main process at least. In this
// case we'll probably create the buffer from a precreated region of memory.
// -----------------------------------------------------------------------------
class BitmapPlatformDevice : public SkBitmapDevice, public PlatformDevice {
public:
    // Create a BitmapPlatformDeviceLinux from an already constructed bitmap;
    // you should probably be using Create(). This may become private later if
    // we ever have to share state between some native drawing UI and Skia, like
    // the Windows and Mac versions of this class do.
    //
    // This object takes ownership of @cairo.
    BitmapPlatformDevice(const SkBitmap& other, cairo_t* cairo);
    ~BitmapPlatformDevice() override;

    // Constructs a device with size |width| * |height| with contents initialized
    // to zero. |is_opaque| should be set if the caller knows the bitmap will be
    // completely opaque and allows some optimizations.
    static BitmapPlatformDevice* Create(int width, int height, bool is_opaque);

    // This doesn't take ownership of |data|. If |data| is NULL, the contents
    // of the device are initialized to 0.
    static BitmapPlatformDevice* Create(int width, int height, bool is_opaque,
        uint8_t* data);

protected:
    SkBaseDevice* onCreateDevice(const CreateInfo&, const SkPaint*) override;

private:
    // Overridden from PlatformDevice:
    /*cairo_t**/PlatformSurface BeginPlatformPaint(const SkMatrix& transform,
        const SkIRect& clip_bounds) override;

    static BitmapPlatformDevice* Create(int width, int height, bool is_opaque,
        cairo_surface_t* surface);

    // Loads the current transform and clip into the context.
    void LoadConfig(const SkMatrix& transform, const SkIRect& clip_bounds);

    // Graphics context used to draw into the surface.
    cairo_t* cairo_;

    // True when there is a transform or clip that has not been set to the
    // context.  The context is retrieved for every text operation, and the
    // transform and clip do not change as much. We can save time by not loading
    // the clip and transform for every one.
    bool config_dirty_;

    DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
    friend class ScopedPlatformPaint;
};

} // namespace skia

#endif // SKIA_EXT_BITMAP_PLATFORM_DEVICE_CAIRO_H_
